vRtrTunnelMask indicates the mask to be logical-ANDed with the destination address before being compared to the value in the vRtrTunnelDest field. For those systems that do not support arbitrary subnet masks, an agent constructs the value of the vRtrTunnelMask by reference to the IP Address Class. Any assignment (implicit or otherwise) of an instance of this object to a value x must be rejected if the bitwise logical-AND of x with the value of the corresponding instance of the ipCidrRouteDest object is not equal to ipCidrRouteDest.